1. Field of the Invention
The present invention relates to an illumination device including with a point light source and a light guide plate, and a liquid crystal display.
2. Description of the Background Art
Various inventions have been made regarding an illumination device that emits light. For example, Japanese Patent Application Laid-Open No. 2006-4645 describes a planar illumination device, which includes a light guide plate and a point light source arranged along the side end surface of the light guide plate, and emits light from the main surface of the light guide plate. The side end surface where the point light source is arranged is provided with a plurality of stripe projections projecting from the side end surface and extending in a thickness direction of the light guide plate, and each of the stripe projections includes a pair of flat surfaces symmetrically inclined in the width direction of the stripe projection and a curved surface connecting the tip sides of the pair of flat surfaces.
According to such an illumination device, light incident on the stripe projection from the point light source is refracted by a structural surface of the stripe projection and dispersed inside the light guide plate in a wide range, so that the light emitted from the main surface of the light guide plate can be made uniform. Furthermore, the surface of the stripe projection includes the pair of flat surfaces symmetrically inclined in the width direction of the stripe projection, and a curved surface connecting the pair of flat surfaces, and since a refraction angle of light incident on the light guide plate from the point light source is different between the flat surface and the curved surface, it is possible to obtain an optimal balance between light diffusion and luminance enhancement.
However, in the planar illumination device described in Japanese Patent Application Laid-Open No. 2006-4645, on the side end surface of the light guide plate that is opposed to the point light source, a front portion of the point light source has high luminance but a portion therebetween has low luminance. This tendency is particularly significant when the interval between the point light sources is large, resulting in a problem in that luminance in the vicinity of the side end surface (light entrance surface) of the light guide plate becomes nonuniform.